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Don Paul: Will frozen waterways give way to floods?

Not exactly a shocker, but the extreme cold we’ve endured has done its thing to Lake Erie.

On Jan. 1, the lake was wide open. The lake temperature was 39 degrees, 4 degrees above average for the date. This is the way the lake looks as of Feb. 1.

Lake Erie is always out in front on icing due to its shallow water. The other four lakes can get plenty of ice, but generally they are not prone to becoming mostly ice-covered. Here is the ice cover analysis from NOAA’s Great Lakes Environmental Research Lab in Ann Arbor:

(NOAA)

Total Great Lakes ice cover has increased by 8 percent in just the last 24 hours — I looked — but only Lake Erie is mostly frozen, with a shrinking amount of open water in the eastern third of the lake. Obviously, Western New York streams and creeks have frozen. Many of you are aware a warmup is on the way, with the potential to melt and break up that ice. That may produce ice jams and ice jam flooding, as shown in this photo from WBFO.

Warming would be the main culprit, obviously, in the ice jam threat. Here is what the hydrology desk at the Buffalo office of the National Weather Service has to say: “Rising temperatures Sunday through next week will significantly elevate the risk of ice jams. Thawing Degree Hours will reach the point where ice may begin to move by Monday. Ice jam concerns would then continue through Thursday. The most susceptible areas to ice jams are the Buffalo Creeks, Cattaraugus Creek and the upper Allegany River, although they can happen anywhere.”

The other ingredient that would raise the flooding risk is rain. Rain would add to the meltwater and runoff. Some limited rain is likely Sunday, but amounts will be minor and will add very little to the runoff, with temps in the low 40s. The seven-day forecast estimate from National Weather Service headquarters for liquid to add to the runoff is more problematic, showing 0.5 inches to 0.75 inches.

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Much of that liquid would reach us later next week. However, by that time the big warmup will have retreated, and it’s possible that precipitation could fall as snow or a mix, as seen in the GFS model. Cooler temperatures at that time would shorten the duration and rate of melting.

The largest snowmelt will occur where the heaviest snow fell, mainly northern Erie and southern Niagara Counties. Even though the snow was lower-density and less water-laden in the frigid temperatures, 20 inches of fluffy snow could still produce a lot of meltwater into the usual culprit creeks, such as Cazenovia, Ellicott, Buffalo and other metro area creeks. So the National Weather Service hydrology folks and municipalities such as Buffalo and West Seneca will have to monitor the situation carefully.

As for the duration and extent of the warmup, it may be less impressive than some folks believe. It peaks Monday, with the warmest day since Jan. 23, when we hit 47. By Wednesday, it looks like we’ll be back in the low to mid-30s, which would certainly slow the melting. After slight warming next Thursday, by Friday we’ll be getting cold and then colder thereafter. Note the polar temps over the northern plains (not currently looking like the brutal cold just past).

As for the overall pattern, the ensembles of models’ upper air flow are in good agreement that milder Pacific air will be flooding most of the lower 48 by Sunday and Monday.

Lest we forget it’s February, some continental polar air is likely to be directed our way heading into the middle of the month.

A scholarly acquaintance, Dr. Judah Cohen, has been doing extensive research on the polar vortex, and he tweeted this while I was writing this article: “Drip, drip, drip. Impacts of #PolarVortex19 continue to slowly drip/bleed down from the stratosphere to the surface into mid-February. Impressive widespread #cold temperatures continue to be predicted across Eurasia and North America second and third weeks of February.”

Some of you heard during the autumn we were headed into an El Niño winter. The oversimplified idea that El Niño equals mild winter has created the wrong impression. As I’ve written several times, statistical research done at National Weather Service Buffalo, specifically by meteorologist Bob Hamilton, has demonstrated weak El Niños generally do not correlate with milder winters in our region.

In fact, the opposite is often the case, with a better correlation for colder and sometimes snowier winters here with a weak El Niño, or a neutral El Niño Southern Oscillation/ENSO, or a weak La Niña. No one variable controls the pattern, but a weak or neutral ENSO — which is what we have — is not associated with an easy winter 'round these parts. (Strong El Niños are another matter, and they do have the warmer correlation, as in the winter of 2016-17.) While statistical probabilities of getting just as cold as what occurred this past week are lower, there is some compelling evidence for a return to below-average temperatures by midmonth and beyond.

In the meantime, Buffalo snowfall is now up to 91 inches, which is 29.5 inches above average and nearly our total cold season average. The National Weather Service estimates there is 2 to 4 inches of liquid stored in our snowpack, at least over northern Erie County. With the temporary warming and possible rainfall, they have just issued a flood watch for all of Western New York, except Allegany County, from late Sunday night through Wednesday night.

People who live in ice-jam flood-prone neighborhoods should begin taking precautions to protect their property and possessions.

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